A fine-scale genetic linkage map reveals genomic regions associated with economic traits in walnut (Juglans regia)

Authors: Aradhya, Mallikarjuna; VELASCO, DIANNE - University Of California; WANG, JI-RUI - Sichuan Agricultural University; RAMASAMY, RAMESH - University Of California; YOU, FRANK - Agriculture And Agri-Food Canada; LESLIE, CHUCK - University Of California; DANDEKAR, ABHAYA - University Of California; LUO, MING-CHENG - University Of California; DVORAK, JAN - University Of California

Submitted to: Plant Breeding Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2019
Publication Date: 5/27/2019
Citation: Aradhya, M.K., Velasco, D., Wang, J., Ramasamy, R., You, F.M., Leslie, C., Dandekar, A., Luo, M., Dvorak, J. 2019. A fine-scale genetic linkage map reveals genomic regions associated with economic traits in walnut (Juglans regia). Plant Breeding Reviews. 138(5):635-646. https://doi.org/10.1111/pbr.12703.
DOI: https://doi.org/10.1111/pbr.12703

Interpretive Summary: A genetic linkage map of walnut containing 2220 single nucleotide polymorphisms (SNPs) in 16 linkage groups (LGs) was constructed using an F1 mapping population from a cross between ‘Chandler’ and ‘Idaho’, two contrasting heterozygous parents. Five quantitative yield traits; lateral fruitfulness, harvest date and three nut traits (shell thickness, nut weight, and kernel fill) were then mapped on to the linkage groups. A significant QTL in LG 11 with negative additive effects suggested heterozygote superiority in the expression of lateral bearing. A set of three QTLs explaining ~10% of the variation in harvest date was located in LG 1. Shell thickness, nut weight, and kernel fill were under the control of two to three linked pleiotropic QTLs in LG 1 segregating from ‘Idaho’. The marginal positive additive effects of QTLs for harvest date, shell thickness, and nut weight and small negative additive effects for kernel fill suggested the QTLs had marginal effect on the expression of these traits.

Technical Abstract: A genetic linkage map of walnut containing 2220 single nucleotide polymorphisms (SNPs) in 16 linkage groups (LGs) was constructed using an F1 mapping population from a cross between ‘Chandler’ and ‘Idaho’, two contrasting heterozygous parents. Five quantitative yield traits; lateral fruitfulness, harvest date and three nut traits (shell thickness, nut weight, and kernel fill) were then mapped on to the linkage groups. A significant QTL in LG 11 with negative additive effects suggested heterozygote superiority in the expression of lateral bearing. A set of three QTLs explaining ~10% of the variation in harvest date was located in LG 1. Shell thickness, nut weight, and kernel fill were under the control of two to three linked pleiotropic QTLs in LG 1 segregating from ‘Idaho’. The marginal positive additive effects of QTLs for harvest date, shell thickness, and nut weight and small negative additive effects for kernel fill suggested the QTLs had marginal effect on the expression of these traits.